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Old 06-01-2013, 04:17 PM   #1
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General diagnostic procedure

Please allow me to rant a little bit, but also offer a systematic approach to problem solving. The inspiration ;-) for this post came from a current thread about the OP's house batteries not charging. After 10 posts, no one offered a diagnostic approach, only suppositions (and as always, quite a few extraneous posts). I posted a sequential procedure that I hope is correct and will lead the OP to find the solution.

But back to the general topic. Most of us have been burned at the hands of mechanics who simply change parts until the problem goes away. Sometimes it takes 2-3 different parts until the problem is resolved. Almost certainly 1 or 2 of those parts was perfectly good. And even worse, maybe the immediate problem was solved, but because no one understood the underlying cause of the problem, the failure happened again.

So when you have a problem whether it is engine, electrical, hydraulic or whatever, stop to think about ALL of the things that could cause the problem. Develop a list and write it down. Then think about how you would confirm or deny that each possible cause was really the cause.

Usually these potential causes will form a chain starting with where the problem is apparant (the dead house battery) and work its way back to where the situation is known to be good (the output of the engine alternator). Electrical problems are often straightforward and linear in their chain up the line.

Engine problems are more complex. An overheating engine has many potential causes, some in a chain (the raw water flow path) and others sort of one off (a fouled heat exchanger, a bad thermostat). But all have simple, low cost diagnostic steps that can be explored.

We all have horror stories and this one wasn't mine, but I was a bystander waiting for it to be resolved so I could close on the boat purchase. After replacing the exhaust elbow, the raw water pump, the heat exchanger, etc and some $2-3,000 later (on a $6,000 engine) the problem was found to be a collapsing raw water suction hose that some previous mechanic had stepped on repeatedly and crushed. The $20 hose was replaced and the engine ran at wot without overheating. A simple bucket test to measure raw water flow out the exhaust would have pinpointed this problem.

So, think about causes and a logical way to eliminate them rather than follow a hit or miss approach.

David
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Old 06-01-2013, 04:47 PM   #2
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Good point! I might also add that it helps to READ and understand the OP before adding advice!
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Old 06-01-2013, 10:25 PM   #3
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=djmarchand;
"So when you have a problem whether it is engine, electrical, hydraulic or whatever, stop to think about ALL of the things that could cause the problem. Develop a list and write it down. Then think about how you would confirm or deny that each possible cause was really the cause.

So, think about causes and a logical way to eliminate them rather than follow a hit or miss approach."


A logical, systematic approach to problem solving based on knowledge and experience.........................that's positively UN Trawler like, a very dangerous concept indeed, and would in all likelihood lead to a sharp decrease in the sale of duct tape and cable ties worldwide.
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Old 06-01-2013, 11:28 PM   #4
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Really great point, David. A thorough understanding of systems including all system components is really needed to even begin a logical approach to troubleshooting.

Often, us armchair mechanics sitting at a keyboard lack the details needed to provide meaningful troubleshooting assistance. But we don't let that stop us from trying to help based upon our own assumptions, past experiences and misunderstandings.

Even with all that stacked against us, once in a great while, one of us gets it right. So now, we each secretly want to be that next guy to be able to 'ring the bell'. We mean well...
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Old 06-02-2013, 12:15 AM   #5
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As a automotive technician specialising in electronics , drivability and HVAC I refuse to work on a vehicle that the service writer puts on the work order tune up or recharge AC.I insist they question the customer what the actual symptoms are the customer is complaining about, I then try to duplicate this symptom so that when I find a fault I can relate it back to the original complaint.Unfortunatley many others donot practice this not just in the trade but in many other trades aswell
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Old 06-02-2013, 07:56 AM   #6
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Really great point, David. A thorough understanding of systems including all system components is really needed to even begin a logical approach to troubleshooting.
Common Troubleshooting Myth:

"You need to be an expert on the machine or system you're troubleshooting" This most destructive myth costs companies millions when they hire the wrong people for the wrong jobs. If you know enough about the machine to know what tests to conduct (and you'd be surprised how little knowledge that is), you can use the Universal Troubleshooting Process to narrow the problem down to the root cause. Often mere possession of the system documentation or service manual gives you enough expertise."
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Old 06-02-2013, 10:43 AM   #7
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March I think you're correct.

But that assumes the purpose of TF is problem solving. At times it is as people ask questions and get answers .... a few good answers and a few bad answers and many that seem rather questionable. We are here for camaraderie and entertainment. Problem solving is there but way down the list I'd say.

We're here to kick things around and have fun. Kinda like the tavern "Cherrs". You went there and talked about your car troubles (kicked them around) and then went home and fixed them or (much more likely) took the car to the mechanic. The most important thing to know about mechanics and similar things is when to tackle it yourself and when to go to the garage.

I'm more serious and less a jokester and when I'd like to have a serious discussion it dosn't last very long most of the time. We have some great jokesters here and that's good as fun and jokes are largely the name of the game but a good discussion can be ruined by good or bad jokes. And of course we have much TC.

And March I had an experience in the Navy troubleshooting electronics. Good logic and troubleshooting methods were heavy on my mind especially since I wasn't a strong technician I had to rely on good methods and logic to do my job. Just stopping and evaluating what makes sense and what dosn't add up leads one frequently to reality. But one can go astray easily w what one thinks is right only to find out your assumptions weren't correct.
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Old 06-02-2013, 12:40 PM   #8
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My experience is you donot need to be an expert on the system, just have a general understanding of how it functions and use a logical diagnostic procedure.I have seen many times people just throw parts at a problem, battery going dead for instance, first a new battery goes in then an alternator and regulator problem still there so then it comes into the shop and it turns out someone plugged something in to the rear powerpoint and forgot to unplug it and a draw on the battery is the problem, 5 mins with a DVOM would have found a draw and a pile of money saved.
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Old 06-02-2013, 01:37 PM   #9
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I remember a long time ago a mechanic diagnosed a car problem and declared it was w the automatic transmission. After a transmission rebuild the problem finally turned out to be a spark plug.

However many a good spark plug has been replaced w a "tune up" thinking a tune up would solve any running issues.

Re what djmarchand says ... peeps just don't think enough and in the right channels.
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Old 06-02-2013, 02:57 PM   #10
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Quote:
Originally Posted by RickB View Post
Common Troubleshooting Myth:

"You need to be an expert on the machine or system you're troubleshooting" This most destructive myth costs companies millions when they hire the wrong people for the wrong jobs. If you know enough about the machine to know what tests to conduct (and you'd be surprised how little knowledge that is), you can use the Universal Troubleshooting Process to narrow the problem down to the root cause. Often mere possession of the system documentation or service manual gives you enough expertise."
I think we're saying the same thing here. Systems knowledge is needed to "know enough about the machine to know what tests to conduct".


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Old 06-02-2013, 04:54 PM   #11
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I think we're saying the same thing here. Systems knowledge is needed to "know enough about the machine to know what tests to conduct".
I thought you wrote:

"A thorough understanding of systems including all system components is really needed to even begin a logical approach to troubleshooting."

Which is a long ways from:

"Often mere possession of the system documentation or service manual gives you enough expertise."
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Old 06-02-2013, 06:44 PM   #12
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Variables Rick Variables.
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Old 06-02-2013, 06:56 PM   #13
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Variables Rick Variables.
Which "variables" might those be?
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Old 06-02-2013, 07:07 PM   #14
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Yeah me too...
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Old 06-02-2013, 10:09 PM   #15
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I agree and disagree with Rick. I think that analytical people can troubleshoot well without expertise. I think that non-analytical people who are experts can absolutely suck at troubleshooting.

I've sat through many a RCA wanting to choke people.

I was fortunate that I had unlimited funding backing my training in the sub force. They taught theory first, then equipment, then systems, then equipment and system operation, then repair and maintenance, then troubleshooting, then advance troubleshooting.

I also happened to be a trainer in that organization for three years. Do you know the saying "There are no stupid questions"? Well if that is true, then what kind of questions do stupid people ask? I know the answer.

The other thing that organization did was test personality types. I've also had to sit with industrial psychologists as well. Every time I'm tested I come up ENTP. I know I am analytical. Troubleshooting for me is fun! Not only that, I get paid to do it!

So that's why I agree and disagree with Rick. I believe he's analytical to, and probably doesn't realize that most other people aren't.
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Old 06-02-2013, 10:42 PM   #16
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Spy,
I am an ENTP too. Possibly an ESTP but the E,T and P are for sure. Did the "industrial psychologists" just psych you or do you have the book "Please Understand Me"?

Rick,
Opinions .... variable opinions. Politicians shine w variable opinions.

Spy wrote,
"So that's why I agree and disagree with Rick. I believe he's analytical to, and probably doesn't realize that most other people aren't."
I resemble that. I go on and on about theories on anchors until I realize I'm alone in the woods talking to myself.
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Old 06-02-2013, 10:50 PM   #17
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I think we're going to need a new Meyers-Briggs Personality Diagnostic Procedure thread so we can all list our MB Test results.
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Old 06-02-2013, 11:21 PM   #18
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Spy,
I am an ENTP too. Possibly an ESTP but the E,T and P are for sure. Did the "industrial psychologists" just psych you or do you have the book "Please Understand Me"?

Rick,
Opinions .... variable opinions. Politicians shine w variable opinions.

Spy wrote,
"So that's why I agree and disagree with Rick. I believe he's analytical to, and probably doesn't realize that most other people aren't."
I resemble that. I go on and on about theories on anchors until I realize I'm alone in the woods talking to myself.
Oh, I got multipage reports...

FWIW, I had you figured for an ESTP, and Rick an ENTJ.
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Old 06-03-2013, 06:38 AM   #19
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However many a good spark plug has been replaced w a "tune up" thinking a tune up would solve any running issues.

Probably 40 years since I have seen a plug either tested or cleaned in a shop.

Cheaper to toss them.

For most non mechanical folks HAVING Da Book on board will be a huge help for whoever will be looking to help.

ITS OK if you don't understand a word of it , just have it!
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Old 06-03-2013, 06:50 AM   #20
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I think we're going to need a new Meyers-Briggs Personality Diagnostic Procedure thread so we can all list our MB Test results.
The results could be scary.
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